Questions tagged [speed-of-light]

The speed of light is a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.

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What would happen if $c$ wasn't constant, but the quotient of $c$ with the scale factor $a(t)$ was? [closed]

I'm supposing there are strong reasons to disregard this scenario but I can't understand exactly what would it imply, and why it is not at all considered in cosmology. What I'm talking about is: we ...
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What is a simple example that contradicts the theory that light (photons) could have a super small mass? [duplicate]

The obvious example is that, to bring something that has mass to the speed $c$ requires infinite energy due to special relativity. But what if a kid asked me "What if light/photos had a super ...
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Is a photon truly massless? [duplicate]

First of all, I am not a physicist or mathematician, not even a hobbyist but the following statements have always puzzled me: $E=mc^2$ A photon is a desecrated particle of energy. A photon is ...
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Physical meaning of $vx/c^2$ in Lorentz transformation

In Lorentz transformation, this is the formula of time dilation $$t' = \gamma \left( t - \frac{vx}{c^2} \right)$$ It can be derivated from the formula of length contraction and be proved ...
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Is there a good quantum explanation of refraction? [duplicate]

I'm aware of the classical explanation of refraction which deals with light being a wave that gets "slowed" down while passing from a medium to another. One problem that I have with this ...
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Black hole production via light speed [duplicate]

As a test particle with rest mass approaches $c$ relativistic mass increases to infinity, does this mean that the energy required to continue the acceleration will create a black hole (as time also ...
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When you are in a gravitational field, do object far away get physically closer to you as you get closer to the mass?

An observer A is close to a black hole and an observer B one light year away. They are both remaining at constant radial distance from the black hole. A is at 2 Rs away from the center of the black ...
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Second postulate of Special Relativity - Finite Invariante Speed?

@JohnRennie, the most decorated physics stack exchange user of all time, answered the question whether the first postulate of special relativity implies the second (Einstein's first postulate ...
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Why is the speed limit of special relativity $C$ equal to the speed of light $c$ and why must there be only one?

DISCLAIMER: this question is different from other questions posted here previously despite accidentally similar titles. This question is not a duplicate of the one linked bc the linked question is ...
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Is a Lorentz transformation allowing an infinite value $c$ still a proper Lorentz transformation?

Is it correct to say that inertial systems are related by Lorentz transformations even if we do not know if the "invariant speed" is finite or infinite? To me, this is incorrect because $c$ ...
1 vote
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What are relativistic particles? [duplicate]

What are relativistic particles? I got it in a question of mechanics. So, what is it about a particle that makes it "relativistic"?
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Phase difference in Michelson Interferometer

I'm currently taking a quantum mechanics course in university and our professor introduced us to the Michelson Interferometer (or at least what I believe is an apparatus based on it), where a light ...
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Special relativity velocity addition formula precision [closed]

I tested the special relativity addition formula $$u_{\text{total}}=\frac{v+u}{1+\frac{vu}{c^2}}$$ and found that addition of small numbers converges to smaller speed, but bigger numbers to bigger ...
1 vote
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Does squeezed light gravitate repulsively? [closed]

Since there are alternate regions of positive and negative energy densities in squeezed light, does that mean that the negative energy density parts gravitate repulsively? Since the stress energy ...
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